Fungal diseases represented by athlete's foot, vaginal candidiasis, and so on were formerly the diseases difficult to be completely cured, so the treatment of athlete's foot has been a theme of eternity.
In recent years, bifonazole and other various drugs such as butenafine and terbinafine have been developed, allowing general cutaneous fungal diseases such as athlete's foot to be completely cured. Among the fungal diseases, however, one invaded in the thickened or excessively keratinized portion of a nail or skin remains almost impossible to be treated with the external application of a drug because of the difficulty of allowing the drug to be transdermally delivered to that portion. Therefore, the treatment of such a fungal disease has been only conducted by means of a method involving orally administering an antifungal agent such as terbinafine for as long as several months. Such oral administration is systemic, so it will involve a great economic burden when it is prolonged. Besides, the above administration has been difficult to be applied on tinea unguium having a little influence on a human life because of an increase in possibility of causing side effects or the like.
In other words, the conventional method has been insufficient to be applied as a therapeutic procedure with external administration of a drug on a fugal disease invaded in the bottom portion of thick keratin such as the inside of a thickened or extensively keratinized portion of a nail or skin. Therefore, development of a medicinal composition useful for an external treatment of the fungal disease invaded in the bottom portion of such thick keratin has been demanded.
On the other hand, the compound represented by the general formula (1) to be described latter has been known to have an antifungal action. However, no technology, which utilizes such a compound as a principal ingredient to prepare an antifungal preparation for tinea unguium or for tinea in the thickened portion of heel or the like, has been known in the art at all.
Furthermore, no idea for obtaining an antifungal medicinal composition by combining the antifungal compound represented by the general formula (1) and a specific film-forming agent or a water-soluble plasticizer in the form of a solid or paste at 20° C. at 1 atm has been known in the art at all. Besides, the fact that the antifungal medicinal composition composed as described above will be useful in the treatment of tinea unguium and the fungal diseases in the excessively keratinized portion or thickened portion of the skin has not been known at all.